We're staying at the Gran Bahia Principe. We were kind of hoping for 2 dives per day, is that expecting too much?
I actually went diving with the Gran Bahia's on-site dive group (ScubAquatic) just a couple of months ago. I also called around to a bunch of the other places. Here's what I ran into:
All of the places I talked to (all in that general area) held two morning dives, and then taught classes in the afternoon. I want to say the first dive is generally around 9 a.m., and the second's around 11, but I'm not 100% sure. I was back at my hotel around by about 12:30, though, and that was after waiting for the shuttle. Oh, and while many of the dive shops list night dives on their websites, I couldn't find any actually holding a night dive.
From what I can tell, all of the dive shops and groups have a schedule for which sites they dive (site A & B on Monday, site C & D on Tuesday, and so on). And if you can figure out a way to get it out of them, please tell me - I tried for weeks in advance, and got nowhere.
Drift diving (just from a random spot) wasn't very impressive. Yeah, there was some coral, and the occasional (small) purple sea fan, but . . . it wasn't quite what I expected from a Carribean dive. Did see a fair amount of fishing cages, though.
One of the more official dive sites was more impressive. We also dived near Pear Tree River (which is a boat dive only -a local nudist colony controls the beach), which was more what I'd been hoping for. Huge walls of coral disappeared off into the deep, and there were several types of soft coral (including impressively large purple sea fans). There's a short coral cavern (maybe 15' long) to swim through, and actual schools of fish.
Oh, and you definitely need to check your depth a lot. The water there is this gorgeous clear blue, with amazing visibility. But that also means its hard to guess your actual depth - I could've sworn I was only 30' down at Pear Tree, for example, and yet the depth gauges were adamant that we hit 80'.
Hope that helps. Oh, and while you're there, I suggest hitting Dunn's River Falls and Luminous Lagoon. Dunn's River is a series of short waterfalls that you can actually hike up, and its one of the signature touristy things to do in Jamaica. And Luminous Lagoon is a bioluminescent bay near Falmouth - there are only a dozen or so in the world, and its much,
much more impressive than the photos imply. Your resort will probably offer trips to both.